Rock drill



If SUZUKI March 19, 1935.

ROCK DRILL Filed Nov. 13, 1933 2 Sheets-Sheet 1 INVENTORI v T 3143 u/(l MA Zk ATTORNEYS.

March 19, 1935. T sUZUKl 1,995,230

ROCK DRILL Filed Nov. 13, 1953 2 Sheets-Sheet 2 ATTORNEIYS.

Patented Mar. 19, 1935 UNITED STATES PATENT! OFFICE Ibaraki, Japan,

assignor 'to Kabushiki Kaisha, Tokyo,

Nihon Kogyo Japan Application November 13, 1933, Serial No. 697,870

Japan August 8, 1930 scams. (01. 12128) This invention is a continuation in part of my prior application Serial Number 553,829 filed July 29, 1931 and certain parts of the subject matter of this invention will be found in the said earlier application andrelates to. a rock drill characterized by the fact that the spool valve loosely mounted on a valve guide axis is arranged in a cylinder which is in alinement with the central line of movement of a piston hammer, and that on forward stroke of the piston, an 'air port for shifting the valve is opened and the supply of live air to back of the piston is stopped at the same time of giving a blow to a drill steel, and thereafter an exhaust port provided in the cylinder wall is opened, while on backward stroke of the piston, another air port for shifting the valve is opened and the supply of live air to front of the piston is stopped and thereafter the exhaust port provided in the cylinder wall is opened.

The'invention is further characterized by that the piston is provided with a ring groove, by means of which the exhaust port in the cylinder Wallis communicated with either one of the air ports for shifting the valve during the major time of piston strokes, so that the valve is moved with least shifting resistance.

The object of the invention is to provide a new rock drill by which the pressure drop in the cylinder is avoided, energy of blow as well as numberof blows is increased, vibration of the machine is reduced, loss of live air and shifting resistance of the valve are minimized, andalso projecting parts of the machine are done away with, all these factors combined contributing to the promotion of working capacity of the machine.

In the accompanying drawings, Fig. 1 is a vertical section of a rock'drill embodying the inventiqn, and Figs. 2 and 3 are views showing diagrammatically the action of the valve.

Referring to Fig. 1, A is a cylinder, B a valve box, D a valve guide axis, H a piston hammer,

45 M, a ring groove provided on the piston, G a drill vided on the piston, R a rifle, bar, 1 and f H the cylinder bearings of the piston hammer,-

valve faces adapted to displace the valve backwards and forwards respectively, P and P air ducts, E and E air exhaust ports for the valve, e and e air exhaust ducts which are in communication with spaces partitioned by the valve 5 faces, 0 an auxiliary exhaust port provided in the cylinder wall for discharging air exhaust directly from the cylinder, b an air port provided with the cylinder wall for supplying air to the front face 1* of the valve through the duct 1) w push the valve backward and also for exhausting air during forward stroke of the valve and c an air port also provided in the cylinder wall for supplying air to the'back face 1" of the valve through the duct c' to push the valve forward and 15 also for exhausting air during backward stroke of the valve, the port 0 being positioned between the ports b and c.

The distance 1 between the centers of the air ports 1) and c is practically equal to the distance 20 2 between the centers of the cylinder bearings H, while the breadth t of the cylinder bearings is notsmaller than the diameter of the ports I) and 0 so that the both bearings can cover the ports b and c at the same time. In Fig. 2, the 25 parts are shown in the positions where, after the valve having been pushed backward, the compressed air enters in the direction of'an arrow a: into the chamber K in front of the cylinder bearings H through the air duct P, and is in the instant to begin to push the piston backward. When the piston is pushed backward and the air port 0 is opened, the compressed air enters therethrough, thereby the rear valve face 1" is pushed forward and thereby the valve is displaced forward. Fig. 3 shows the position where the valve is in forward position and the piston is just reversing its direction of stroke. At this instant the compressed air enters through the compressed air supplying duct a as shown in the direction of an arrow 1 into the chamber K in back of the cylinder bearings H' through the air duct P, thereby pushing the piston forward. When, after the piston has been pushed forward, the air port b is opened, thecompressed air enters therethrough, pressing the front valve face 1, and let the valve return to its original position as shown in Fig. 2. g

As explained above, by the reciprocating movement of the valve V and the piston hammer H attains reciprocating stroke, giving thereby a blow to the head of the drill steel G, and completing the drilling operation, as desired.

According to the invention, the arrangement of the parts being as above explained the cylinder bearings H move backward or to the right from the position shown in Fig. 2, opening the air port c and moving the valve V to the left, causing the connection between the air ducts a and P to be interrupted, and therefore, by this means the live air is prevented from escaping through the port 0, while the exhaust air contained in the front chamber K is rapidly discharged through the passage P' -E and also through the port 0 with the result that the air pressure resisting the forward stroke of the cylinder bearings H to the left is quickly diminished, so that very quick forward stroke is subsequently attained. Further when the cylinder bearings H move forward from the position shown in Fig. 3 or to the left into the position shown in Fig. 2, giving a blow to the drill steel and also causing the compressed air from the air port I) to move the valve.

to the right, the connection between the air ducts a and P is stopped, and thereby the live air is prevented from escaping through the port 0 and air in the back chamber K is rapidly discharged through the passage P-E. On the other hand, from the fact that the cylinder bearings H, after having given a blow to the drill steel at the position shown in Fig. 2, and having moved to the left near to shunk head, firstly opens the auxiliary exhaust air port 0, it is obvious that in the instant of giving the blow the port 0 remains closed, and thus maintains the air pressure not dropped, so that an immense energy of blow can be preserved. On the completion of the opening of the port 0, the supply of the live air is stopped, and hence no live air escapes through the port 0, while the piston hammer is enabled to be quickly pushed backward due to the pressure drop caused instantly by the opening of the port 0. As to the above description, it is noted that when the cylinder bearings H move to the left from the position shown in Fig. 2, the left end of the duct P as shown is once closed, however, the same end, when the cylinder bearings H again move to the. right under the,action of the compressed air in the chamber K, can be again opened. Further the most important feature of the invention is that the cylinder bearings H are provided with a ring groove M and that the relations between the dimensions l, l and t are before mentioned. Suppose the cylinder bearings H are moved backward, then the ring groove M communicates the air port b and the exhaust port 0 at the same time I when the live air supplying ports 0 is opened, so.

that at the same time when the valve face f is pushed by live air, the other valve face I is communicated to atmosphere through the ports b, M and 0 together with through e. Similarly, when the port b acts as live air supplying port and the valve face .1 is pushed by live air, the other valve face I is communicated to atmosphere through the ports 0, M and 0 together with through e. This communication through the ports b, M and O or c, M and 0 possibly decreases the back pressure of the shifting valve and will even produce a pmtial vacuum at the back of the valve when the cylinder bearing of the piston hammer passes through the ports b, c and O with large speed so that it makes valve motion exceedingly sensible and greatly increases the shifting speed. In the known spool valve the valve faces are communicated to atmosphere through very small ports so that the resistance projecting parts of the machine are eliminated, I

and a smooth drill can be obtained.

2. In the known construction, the spool valve and the piston hammer are arranged one above the other, so that they work independently from each other resulting in a violent vibration of the rock drill, and also inconveniences are felt in the handling thereof. Besides, the miners are very rapidly tired in their work. According to the invention, the arrangement of the valve on the cylinder which is in alinement of the piston hammer causes the piston hammer and the valve move together on a straight line so that practically no vibrations occur in the rock drill.

3. The spool valve employed in the known rock drill, or the known heavy drifters has generally a diameter of about 25 to 38 mm., and the number of blows 1000 to 1500 per minute, and

thus is inferior in this point to flapper or tubular valve which has the number of blows of 1500 to 1900 per minute. It is from this reason that the diameter of the spool valve must be increased. However, if the same is greatly increased, it results inincreasing the size of the valve box mounted on the cylinder, and also corresponding inconveniences occur in the manufacture and also in the handling of the rock drill. According to the invention the valve is arranged on the cylinder itself so as to give a relatively great diameter to the valve, and by this means thevalve face is naturally increased. These conditions, together with the arrangement of the 4. According to the invention, the displacement of the valve is much shortened corresponding to the increase of the diameter thereof.

5. From the necessity that the diameter of the valve must be made large while its displacement small in order to increase the number of blows, and for attaining a quick discharge of the air exhaust from the cylinder, it is of general practice inthe known drillcomprising a spool valve proper, that the exhaust from the cylinder is repeatedly passed to the valve box. The invention offers an improvement whereby a direct discharge of the exhaust from the cylinder to the atmosphere is made possible through the auxiliary exhaust air port provided in the latter. auxiliary exhaust port rapidly reduces the back pressure of the valve at the time of its shifting through the ring groove of the piston hammer. This advantage combined with the above mentioned actions enable to remarkably increase the number of blows of the piston hammer of the invention.

6. A rock drill in which an auxiliary exhaust air port cooperates with a spool valve is known. In such construction, however, there is a defect that the live air is wasted owing to the fact that in This . exhaust air from the back portion of the cylinder unnecessary, by making both the diameter of the valve and the exhaust port communicated with the back side of the cylinder sufiiciently large, and also by making the port length considerably short. According to the invention the auxiliary exhaust air port is firstly opened when the piston hammer at the forward stroke has reached to such an extent to give a blank blow, and from this fact it results that the discharge of exhaust air from the back side of the cylinder may more quickly be realized, and thus the pressure is reduced more quickly, so that the air cushioning in the front of the cylinder bearings is promoted. At this instant, the communication of air ducts through the valve is inversed, and therefore there is no fear of the live air escaping as waste from thelauxiliary exhaust air port.

I In the backward stroke of the piston hammer, the closing of the valve is completed before the opening of the auxiliary exhaust air port, and therefore in this case the advantage of meeting no loss of live air is also obtained. That is to say, the auxiliary exhaust air port is firstly opened after the piston hammer has moved further under inertia. It is resulted from this that a quick discharge of exhaust air is made possible, the back pressure in the case of the forward stroke of the. piston hammer is reduced, while the air cushioning necessary for the backward stroke of the piston is still sufliciently kept. All

these conditions coming together may contribute to the increase of the efliciency and number of blows of the spool valve according to the invention.

From the foregoing, it is to be noted, above all, that the loss of live air is minimized according to the invention, and it is experienced that the efficiency of the rock drill according to the invention is increased by 30 percent or doubly as compared with the heretoknown drill.

What I claim is:

1. A rock drill comprising a cylinder, a piston hammer s'lidably mounted therein, adjacent one end thereof, a central guide axis arranged inalinement with the central line of movement of the piston hammer, a spool valve loosely mounted' on the guide axis, an air port provided in the cylinder wall for supplying air to push the valve backward and also for exhausting air during forward stroke of the valve, another air port provided in the cylinder wall for supplying air to push the valve forward and also for exhausting air during backward stroke of the valve, a large exhaust port provided in the cylinder wall be- .tween the air ports, said piston hammer having a ring groove to leave cylinder bearings at the ends of the hammer, said groove acting to communicate the saidexhaust port to either one of the said airports during each piston stroke, the

distance between the centers of the air ports being practically equal to the distance between the respective centers of the cylinder bearings of the piston hammer,.while the breadth of the cylinder bearings is substantially the same as the diameter of the air ports.

2. A'rock drill according to claim 1, wherein the spool valve is of large diameter, and the ports are of large size relatively to the stroke of the valve.

3. A smooth rock drill having practically no projecting parts, comprising the combination of a cylinder, a piston hammer reciprocating therein and having a piston provided with a ring groove to leave cylinder bearings at the respective ends thereof, rotating means for the drill steel including a rifle bar, a valve box mounted by the latter and positioned within the box and arranged on the center line of movement of the piston, distributing and exhaust passages provided in the cylinder wall between the valve box and the cylinder and controlled by the valve, an air port provided in the cylinder wall for supplying air to the front face of the valve to push the valve backward and also for exhausting air during forward stroke of the valve, another air port providedin the cylinder wall for supplying air to the back face of the valve to push'the valve forward and also for exhausting air during backward stroke of the valve, communication passages between the air ports and the respective ends of the valve box controlled by the piston for admitting air under pressure and exhausting the expanded air alternately to and from the respective ends of the box for shifting the valve, a large exhaust port provided in the cylinder wall between the air ports for exhausting air to the atmosphere from the cylinder, the ring groove acting to communicate the large exhaust port with either one of the air ports during each stroke of the piston, the distance between the centers of the air ports being practically equal to the distance between the respective centers of the cylinder bearings of the piston hammer, while the breadth of the cylinder bearings is substantially the same as the diameter of the air ports. 

